重构长try-except链

Question

我有一种感觉，这个序列可能写得更短：

dim = Dimension.objects.get(pk=rows['pk'])
try:
    dim.name = rows['name']
except KeyError:
    pass
try:
    dim.external_flg = rows['external_flg']
except:
    pass
try:
    dim.ext_owner = rows['ext_owner']
except KeyError:
    pass
try:
    dim.ext_table_name = rows['ext_table_name']
except KeyError:
    pass
try:
    dim.ext_start_date_column_name = rows['ext_start_date_column_name']
except KeyError:
    pass
try:
    dim.ext_end_date_column_name = rows['ext_end_date_column_name']
except KeyError:
    pass

我从来没有任何Python代码优化和处理异常的经验，但我很高兴能有一个替代的例子如何缩短它。

谢谢!

Answer 1

使用dict.get()方法：

dim.name = rows.get('name', dim.name)

或者，对于更干燥的解决方案，将所有赋值放入循环中：

for field_name in ('name', 'external_flg', 'ext_owner', 'ext_table_name',
                   'ext_start_date_column_name', 'ext_end_date_column_name'):
    if field_name in rows:
        setattr(dim, field_name, rows[field_name])

要处理list数据，可以使用类似的循环：

for i, field_name in enumerate(('name', 'external_flg', 'ext_owner',
                                'ext_table_name', 'ext_start_date_column_name',
                                'ext_end_date_column_name')):
    if i < len[rows]:
        setattr(dim, field_name, rows[i])

Answer 2

这样的代码应该是有效的--这个答案包含了try/catch块来捕获KeyError :-)

attributes = ['name', 'external_flg', 'ext_owner', 'ext_table_name',
               'ext_start_date_column_name', 'ext_end_date_column_name']

dim = Dimension.objects.get(pk=rows['pk'])

for attr in attributes:
    try:
        setattr(dim, attr, rows[attr])
    except KeyError:
        pass